Filamentous E.coli

Dear experts,
Recently I cloned a pneumococcus gene into an E. coli
plasmid(pUC-derived)(the gene has its own promotor). When trnasforemed
into E .coli, E .coli displayed a much slower growth. When I view it by
LM, and found it becomes filamentous. Most of E.cli are 3-4 times longer,
10-20% of E coli become more than 10 times longer. This is an unexpected
results.
Can somebody there tell me some hints about this, it's really weird.
Rich